In modern oceans, this genus is represented by five species (Compagno, 2005), one off South Africa and the others relegated to the Pacific rim. TRIAKIDAE, the Houndsharks, is a large family, which includes genera such as Mustelus, Triakis, Galeorhinus and the fossil genus Palaeogaleus. These are generally small to moderately-sized, bottom dwelling, often schooling, coastal sharks of temperate and warm seas. Most characteristics used to differentiate members of this family are not captured in the fossil record: the relative sizes of the second dorsal fin or caudal lobe, eye detail, or snout shape. There are features of the teeth which are relevant, even when working with extant specimens.
Triakis maculata KNER & STEINDACHNER, 1866,
The Spotted houndshark is a medium-sized (to 240 cm) little known shark from the temperate waters of coastal Peru, northern Chile and the Galapagos. It is described by Compagno as a very stout shark with a short, rounded snout and broad fins.
According to Herman, et al (1988), T. maculata has a broad-based, Squatina-like cusp with a low distal cusplet. The deep nutrient groove may have two foramina (as represented in the below specimen) and there are abundant foramina on the labial and lingual root faces.
Cappetta (1987) discusses this genus, noting that the anterior teeth are symmetrical with erect crowns, and the laterals, asymmetrical with distally directed crowns. The teeth may have either lateral cusplet(s) or smooth shoulders. He points out that the crown is rather thick and the labial face has a prominent bulge adjoining (/overhanging) the root. The root is expanded with a flat basal face, deep median groove and numerous margino-lingual foramina. He discusses:
T. angustidens CAPPETTA, 1973, Miocene of France
T. ruetimeyeri CASIER, 1958, Palaeocene - West Indies
T. wardi CAPPETTA, 1976, Ypresian - England.
Noubhani & Cappetta (1999) described two new species from the Palaeocene of Morocco, T. antunesi (Thanetian) and T. tanoutensis (Danian).
Kent (1999) includes T. wardi in the Ypresian fauna of Virginia.
The Aquia - Palaeocene of Maryland
When working smaller Piscataway member (Thanetian) sediments, Triakis teeth
can be regularly found. Some of these teeth (Fig ) are markedly similar to T. antunesi, a Thanetian species from Morocco. Without sufficient material to determine if more than one Triakis species is present, it would be premature to assign these teeth to a particular species at this time.
The Nanjemoy - Eocene of Virginia
When adding the Nanjemoy fauna page, this author originally included as Scyliorhinus, small S. gilberti-like teeth. In reviewing material from the Grier collection, Cappetta (as did Kent) suggested that these teeth were much more Triakis-like. Noubhani (pers com 2001) viewed images of this material and concurred that that they appeared to be Triakis, species to be determined.
Miocene of California
Careful picking of Round Mountain Silt sediments from Sharktooth Hill will sometimes yield small triakid-like teeth (Figs.
& ) which are reminiscent in tooth-design with Triakis scyllium MÜLLER & HENLE, 1839.
Cappetta, H., 1987. Chondrichthyes II. Mesozoic and Cenozoic Elasmobranchii. In: Handbook of Paleoichthyologie, vol. 3b, Gustav Fischer Verleg, Stuttgart, 193 pp.
Compagno, L,, Dando & M., Fowler, S., 2005. Sharks of the World. HarperCollins, 368 p.
Herman, J., Hovestadt-Euler, M. and Hovestadt, D., 1988. Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites in living supraspecific taxa of chondrichthyan fishes. Bulletin de L'Institut Royal des Sciences Naturelles de Belgique, Biologie. Part A: Selachii. No 2a: Order: Carcharhiniformes - Family: Triakidae., 58:99-126
Kent, B., 1999. Sharks from the Fisher/Sullivan site. In: Weems and Grimsley (eds) Early Eocene Vertebrates and Plants from the Fisher/Sullivan Site (Nanjemoy Formation) Stafford County, Virginia. Virginia Division of Mineral Resources, Pub 152. pp 11-51.
Noubhani, A and Cappetta, H., 1997. Les Orectolobiformes, Carcharhiniformes et Myliobatiformes des Bassins à phosphate du Moroc (Maastrichtien-Lutétien basal)., PalaeoIchthyologica 8, München. 327 pp
Purdy, R., Schneider, V., Appelgate, S., McLellan, J., Meyer, R. & Slaughter, R., 2001. The Neogene Sharks, Rays, and Bony Fishes from Lee Creek Mine, Aurora, North Carolina. In: Geology and Paleontology of the Lee Creek Mine, North Carolina, III. C. E. Ray & D. J. Bohaska eds. Smithsonian Contributions to Paleobiology, No 90. Smithsonian Institution Press, Washington D.C. pp. 71-202.